The present invention generally relates to electronic displays and, more particularly, to an electrode pattern for a variable-color electro-optic display. The electrode pattern of the present invention consists of multiple sets of electrodes formed into unit cells which are arranged in a sequence and connected in parallel fashion without the need for surface-mounted crossovers.
Color display devices are undergoing an evolution to achieve smaller size and lower power consumption while striving to retain the variable color and resolution qualities of the old CRT (cathode ray tube) technology. One rather new material that is seeing increasing use in color display devices is PLZT (lead, lanthanum, zirconium titanate). This material, having unique physical properties with respect to the passage of light, is capable of electrically controlling either its birefringent (or double-refraction) effect on light to produce color, or its light transmission properties to create an electronic shutter. This is because the optical properties of the material are dependent on an applied electric field, and the electrodes provide the means to individually control the optical properties of locally small areas, or unit cells, of the bulk material. Depending on which effect is desired, as well as the type of information to be displayed, determines how the electrode pattern is implemented and controlled.
Several implementations of solid-state electronic displays are known. A known first implementation utilizing the on-off properties of PLZT incorporates conductors placed into parallel cuts in the material to provide a light shutter. However, while this implementation recognizes that the PLZT may be used for providing a differential phase retarcation and hence implies voltage-variable color, the implementation explicitly discloses the use of PLZT only as a light switch. Moreover, the fabrication process is costly and time-consuming.
A known second implementation utilizing semiconductor technology produces variable color in an active display. This implementation uses a three-dimensional electrode arrangement to control three semiconductor light emitting diode areas for effecting an emissive variable-color display. However, this is distinguishable from the passive approach of the present invention.
A known third implementation first produces color in an active section of a display and then utilizes the birefringent properties of PLZT in a passive section to control the display of variable color. However, this arrangement utilizes dual sets of electrodes mounted on both surfaces to achieve full color variability. Moreover, a single set of electrodes mounted on one surface would have limited color variability.
Thus each of these known prior art implementations falls short of achieving a truly variable passive color display, capable of saturated color, while having a simplified electrode pattern.
Accordingly, there exists a need for further improvement in the implementation of a variable-color PLZT display such that it is truly variable and capable of saturated color while having a simplified electrode pattern which is repeatable without requiring surface-mounted crossovers.